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Shed roof insulation

user-7764336 | Posted in Energy Efficiency and Durability on

Hey – I think I’m on the right track here but just need some confirmation before I go down the wrong path.  So the previous owner added an addition on the back of the house with a shed roof.  This caused serious hot/cold since it was done with open soffits and it just ran right up the side of the house.  I am trying to tighten up the home as I go.  I eventually want to have a continuous layer of 2″ rigid foam on the exterior of the house – we live in Zone 4A and I believe I remember hearing on a BS+Beer show 2″ of rigid foam is enough to keep the dew point outside of the wall assembly on almost any climate zone.

Ok – so I had a roof done about 1-2 years ago and had the contractor put a cor-a-vent like system to allow the roof sheathing to channel air.  I then installed polyiso baffles to channel the air from the soffit to the roof vent.  It gets a little tricky because there is a bulkhead/soffit where the original house and addition meet which has HVAC running through it.  So even if I blocked off the exterior soffit, the sheathing behind the shed roof would still heat up to the temperature of the shed roof “attic” and channel through that interior soffit/bulk head.  I basically blocked off all I could with 2″ rigid foam and then ran 2″ rigid foam up the sheathing (the green lines indicate where I put rigid foam).  Next I am going to fill the joist bays with mineral wool.

I am just looking for some feedback/confirmation that I am not going to cause some unforeseen issues with dew point/amount of foam.

Any advice is helpful – thanks in advance!

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